Spark plug



Oct. 17, 1944. c. E. BERSTLER 2,350,390

SPARK PLUG Filed Sept. 16, 1941 IN VENT OR.

Patent ed Oct. 17, 1944 UNITED STATES PATENT OFFICE" 2,360,390 SPARK PLUG- Carl E. Berstler, Reading, Pa. Application September 16, 1941, Serial No. 411,000 3 Claims. (Cl. 123-169) My invention relates to spark plugs, and particularly to means for improving the operation and increasing the resistance to breakdown thereof.

A spark plug, of any of several standard types,

gasket or to the shell near the gasket, such breakdown being more likely to occur in modern high compression engines.

Also, heating of the center electrode is" excessive by reason of its section and material in relation to the heat insulating dielectric body through which it extends.

Among the objects of the invention is to prevent breakdown of a sparkplug at the inner gasket zone of its shell, between the latter'or the gasket and the center electrode.

Another object is to providean electrode arrangement also tending to increase resistance to breakdown at the gasket zone, and having other novel function and advantages.

In practicing the invention in one form, a spark plug insulator, otherwise of standard type having a body portion, and inner and outer lengths of reduced diameter projecting therefrom, is provided with a groove in the transverse inner end surface thereof around the inner end length.

By such arrangement, or its equivalent, both the capacity and surface creepage paths from the central electrode to the gasket, or the shell adjacent to the gasket, are substantially increased, whereby the resistance to breakdown is greatly enhanced.

A novel electrode for decreasing the heat of the parts at the gasket zone, and of other parts, may effectively take the form having an inner end length of electrode material of usual diameter, and an outer end length of greater diameter, ir respective of its adaptability as one of the elements of a spark gap.

In particular, it is contemplated that the inner end length shall be short and welded, or otherwise secured to, or surrounded by, an outer end length of higher heat conducting material, such as copper.

Such arrangement increases the resistance to breakdown of the plug from overheating, thereby enhancing the action of the above-mentioned groove in the body, and conserving the electrode material.

The single figure of the accompanying drawing is a side view, in longitudinal central plane section, except for the electrodes shown in elevation. of a spark plug embodying only one form of the invention, merely by way of example.

An outer metal shell 2 is generally of usual standard form in having a body portion 3, a portion 4 of nut-like contour for screw threadably mounting the plug in position, an upper crimped flange 5, and a tubular screw threaded firing-end extension 6 of reduced diameter carrying a ground electrode 1.

The shell 2, in this instance, has a flat plane inner end gasket seat 8, normal to the plug axis, surrounded by a surface 9 forming an opening converging into the aperture of the extension 6.

A dielectric element or insulator l0, known as a porcelain, is also generally of usual form having a body portion H in the body 3 of the shell, an outer end length l2 of reduced diameter projecting from the body and the shell, and an inner end length or tip It, also of a diameter reduced from that of the body projecting into the extension 6.

The porcelain III, in this instance, also has a plane shoulder l5, at the underside of the body ll, parallel to, and opposite, the gasket seat 8 in the shell, surrounding, and set off from the main porcelain body proper, by a groove l6. This groove, as shown, is rectangular in cross section, having one side coextensive with the outer side of the tip 14, although such side may be set off from the tip surface and the cross section have other shape.

A gasket I1 is of substantially fluid impervious material, such as copper or compacted asbestos impregnated with a binder, and, in the use shown, capable of flowing under the pressures employed in crimping the shell flange 5 onto another gasket l8 over the top edge of the porcelain body II.

The gasket H, in this case, is narrow between its inner and outer perimeters, and of substantial thickness, whereby to provide a good seal between the seat 8 and the shoulder l5.

Formation of the shell surface 9 removes metal from the critical gasket zone, thereby further conducing to better electrical characteristics, and facilitating the insertion of the porcelain into the shell.

An inner or central electrode 20 has a short inner or firing-end length 2| of small diameter and of good spark-resisting electrode material. This length, in this instance, is welded or otherwise attached in end-to-end relation to a good electrical and heat conductor 22, such as copper, the porthe top of the thread 24, and a screw threaded portion 26 of reduced diameter for the reception 01' a usual terminal cap 21.

The portion 25, in coooperation' with cement or the like, assists in further sealing the plug, and

a position surroundedby said engine mounting section and spaced radially inwardly from said seat portion to therewith form a groove such that acts as a seat for the terminal 21 protecting the porcelain.

By this arrangement, in addition to the advantages stated, the electrode 20 very greatly conserves the amount of its electrode material required, over the amount employed in the usual plug, and further materially improves the cool ing of the electrode and the plug in a manner of particular value at the zone 01' the gasket II.

The line of usual breakdown is apparently through the porcelain about on a line from the gasket I! to the electrode length 2|. In the ordinary insulator, this line is direct, and entirely in the porcelain, between the gasket and the electrode.

By the provision of the groove IE, or its equivalent, this direct line is interrupted, and capacity current forced to travel along a much longer path. The surface creepage distance at this zone is also increased, both by the groove and bya dielectric gasket 01 the type indicated.

The invention is such, as proved in practice, that although it retains substantially all of the sturdiness, ease and economy of manufacture, and other advantages of the best standard plugs, it has higher resistance to the breakdown stated and, in general, performs notably better, so that it i a material advance in the art.

Although the invention is shown in a particular form, changes may be effected therein without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. A spark plug comprising a shell having a body section, an engine mounting section, and

an annular inner shoulder adjacent to adjoining portions of said sections, ground electrode means adjacent to the inner end of said mounting section, inner electrode means cooperating with said ground electrode means to form arcs adjacent to said inner shell end only, and an insulator around said inner electrode means in the shell having an annular seat portion over said shoulder and a portion of reduced diameter ex tending longitudinally 01' the plug inwardly from a line extending transversely of the longitudinal insulator axis between said seat portion and said inner electrode means and traversing said groove is located at a distance greater than the length of said engine mounting section longitudinally outwardly of the plug from said ground electrode means.

2. A park plug comprising a shell having a body section, an engine mounting section, and an annular inner shoulder adjacent to adjoining portions or said sections, ground electrode means adjacent to the inner end of said mounting section, inner electrode means cooperating with said ground electrode means to form area adjacent to said inner shellend, and an insulator around said inner electrode means in the shell having an annular seat portion over said shoulder and a portion oi reduced diameter extending longitudinally of the plug inwardly from adjacent to the outer end of said seat portion and spaced radially inwardly from said seat portion to therewith form a groove such that a line extending transversely of the longitudinal insulator axis between said seat portion and said inner electrode means and traversing said groove is located at a distance greater than the length of said engine mounting section longitudinally outwardly of the plug from said ground electrode means.

3. A spark plug comprising a shell having abody section, an engine mounting section, and an annular inner shoulder adjacent toadjoining portions of said sections, ground electrode means adjacent to the inner end or said mounting section, inner electrode means cooperating with said ground electrode means to form arcs adjacent to said inner shell end, and an insulator around said inner electrode means in the shell having an annular seat portion over said shoulder and a portion of reduced diameter extending longitudinally of the plug inwardly from adjacent to the ,outer end of said seat portion to a position surrounded by said engine mounting section and spaced radially inwardly from said seat portion to therewith form a groove such that a line extending transversely of the longitudinal insulator axis between-said seat portion and said inner electrode means and traversing said groove is located at a distance greater than the length of said engine mounting section longitudinally outwardly of the plug from said round electrode means.

CARL E. BERS'ILER. 

